In the before and after example you provide, the short "sentences" are inconsistently combined with the nearby longer ones. The first two cases are prepended to the following longer sentences. The next two cases are appended to the previous longer sentences. It does not sound like a job for a simple automated joiner.

You know that you will further edit these and assert that it will be easier to edit them when they are combined.

I disagree that it will be easier to edit them when combined. I think it will be harder to locate the joining mistakes that way. At least now there is a visual cue that something is wrong there.

I think what you need are tools for faster human editing.

If you want to do the editing inside FileMaker I think adding a script that can be invoked with a keystroke will help.

This script would join the sentences on either side of the cursor or, if there is a selection, it would join the selection into one sentence.

Of course you will want to create similar keystroke-connected scripts to do each of the other tedious editing tasks. The human then takes on the role of just identifying the problem spots while the computer does the time consuming text editing to fix the type of problem identified.

For this type of task, a customizable text editor or even a word processor with a grammar checker may be a better choice. Copy the text out of FileMaker (if it is there to start) and into the text editor. Do the editing. Then copy it into FileMaker.

You say that you want to remove the commas, but your text has periods rather than commas.

I think that it would be easier to edit if you put the cursor after the period and tapped a button to merge just the two sentence fragments on either side of the cursor by deleting the period and changing the case.

You're missing the period in the very first two words in your "should be" portion or I just don't understand the rules.

For example, handling/parsing:

The more you can contribute their the I think the.

Better.

Tom.

would be problematic based on your desired results.

I tried to code up something from your source text to match your desired text, but ran into inconsistencies between what you do with periods, for example, making this conversion code very difficult (if not impossible). Didn't have more than 30 minutes to work with this.